High performance elevators require direct coupling between a motor and drive sheave in order to provide smooth, low vibration performance. The lack of a gearbox requires the machine to produce high torque at low operating speeds relative to industrial machines of the same power output rating. This results in motors that are large and expensive relative to industrial machines of the same power output.
The size and cost of conventional high-performance gearless machines makes it impractical to implement them in rope-climbing elevator designs, which are desirable for various reasons including optimization of hoistway space and convenient accessibility. Geared machines are undesirable for certain applications such as rope-climbing systems because they introduce vibrations and inefficiencies.
It is an object of the present invention to provide an elevator machine that includes the output and low vibration benefits of a high performance machine, while providing a lightweight and efficiency benefits of a gearless machine. This and other objects are achieved by the embodiments described herein.
The machine of the present invention utilizes a counter-rotating design that doubles the torque applied to lift an elevator for a given size motor, resulting in a motor that is approximately half the size of a motor used on a conventional, direct drive machine for the same duty. The use of counter-rotating drive sheaves eliminates reaction torque on the machine room floor, reducing structural requirements. This is due to the application of both the driving torque and the reaction torque to the elevator, compared to the application of the reaction torque to the machine room floor or other structure as with conventional machines. The machine is of sufficiently reduced size to be mounted on the counterweight and it eliminates reaction torque on the guide rails.